I have a table which stores information on standings in multiple leagues, think of this as a fantasy site. The structure is as follows in terms of columns.
league_id | user_id | total_points | prediction_difference | current_position | last_position
In order to calculate the current standings I am issuing the following query:
SELECT
*
FROM f_u_standings
WHERE league_id = 1
ORDER BY total_points DESC,
prediction_difference DESC
My question is, now I have this result set, how can I then perform an UPDATE based on the SELECT query which updates the current_position column? My programming language of choice on this project is PHP.
you can update with a select.. this assumes you have an ID for each row
UPDATE TABLE f_u_standings fs,
(
SELECT
*
----- do what you want to change current_position -----
FROM f_u_standings
WHERE league_id = 1
ORDER BY total_points DESC,
prediction_difference DESC
) temp
SET fs.current_position = temp.current_position WHERE fs.id = temp.id
This may be closer to what you need:
UPDATE f_u_standings fs,
(SELECT #rownum:=#rownum+1 rownum, id
FROM f_u_standings, (SELECT #rownum := 0) init
WHERE league_id = 1
ORDER BY total_points DESC,
prediction_difference DESC) temp
SET fs.current_position = temp.rownum
WHERE fs.id = temp.id
Related
I am not even sure if this has been answered because I don't even know how to coin the problem. But here is what am trying to do.
I am using COUNT() to create a tabular representation of a data from top to bottom for a 30 day period.
SELECT id FROM table WHERE col = '123' AND date >= DATE_SUB(CURRENT_DATE, INTERVAL DAYOFMONTH(CURRENT_DATE)-1 DAY) AND date <= LAST_DAY(CURRENT_DATE) GROUP BY id ORDER BY COUNT(id) DESC
And I get the result with the most at the top
id | col
==========
id3 | 123
id5 | 123
id2 | 123
id4 | 123
id8 | 123
id5 | 123
id1 | 123
id9 | 123
id7 | 123
This works fine for a tabular view and I can use ol to create a numbering system from 1 - 10. My issue is, I want to be able to tell the position of any given id. Eg. if I want to get the position of id9 in this count result i.e. 8, how do I do that?
If you are using MySQL v8.0 or higher you can use the RANK function:
SELECT COUNT(*), RANK() OVER (ORDER BY COUNT(id) DESC) AS r FROM table GROUP BY id ORDER BY COUNT(id) DESC;
For previous version of mysql, you need to create the variable your self:
SELECT COUNT(*), #rank := #rank + 1 AS r FROM table, (SELECT #rank := 0) temp ORDER BY COUNT(id) DESC;
Note SELECT #rank := 0 initiate the variable.
Updated:
To select a specific id and it's rank, you can use:
SELECT * FROM (
SELECT id, COUNT(*), RANK() OVER (ORDER BY COUNT(id) DESC) AS r FROM table GROUP BY id ORDER BY COUNT(id) DESC
) ranked WHERE id = ?;
Duplicate this table: User_Posts
ID | Upvotes | Downvotes | CAT |
___________________________________
42134 | 5 | 3 | Blogs|
------------------------------------
12342 | 7 | 1 | Blogs|
-------------------------------------
19344 | 6 | 2 | Blogs|
------------------------------------
I need to get the rank of an item within it's category. Therefore ID: 19344 will have Rank position 2, with 4 upvotes, behind 12342 with 6 upvotes. Rank is determined by (upvotes-downvotes) count within it's category.
So I wrote this MySQL query.
SELECT rank FROM (SELECT *, #rownum:=#rownum + 1 AS rank
FROM User_Posts where CAT= 'Blogs' order by
(Upvotes-Downvotes) DESC) d,
(SELECT #rownum:=0) t2 WHERE POST_ID = '19344'
Returns to me (Rank = 2) when run directly in mysql. This is the correct result
However when I try to build it out through code-igniter's query builder I get the
$table = 'User_Posts';
$CAT= 'Blogs';
$POST_ID = '19344';
$sql = "SELECT rank FROM (SELECT *, #rownum:=#rownum + 1 AS
rank FROM $table where CAT= ?
order by (Upvotes-Downvotes) DESC) d,
(SELECT #rownum:=0) t2 WHERE POST_ID= ?";
$query= $this->db->query($sql, array($CAT,$POST_ID))->row_array();
returns to me an empty result: array(rank=>);
so then my question is... but why?
I will also accept an answer will an alternative way to run this query from code-igniters query builder, but ideally I would like to know why this thing is broken.
I've had a similar issue in the past, turns out I had to initialize the variable with a separate query first, I am not sure if this is still the case, but give it a try anyway.
//initialize the variable, before running the ranking query.
$this->db->query('SELECT 0 INTO #rownum');
$query= $this->db->query($sql, array($CAT,$POST_ID))->row_array();
Exactly I don't know why your code is not working. I wrote another solution it will work. Try below code.
$select="FIND_IN_SET( (upvote-downvote), (SELECT GROUP_CONCAT( (upvote-downvote) ORDER BY (upvote-downvote) DESC ) as total FROM (User_Posts))) as rank";
$this->db->select($select,FALSE);
$this->db->from('(User_Posts)',FALSE);
$this->db->where('ID',19344);
$this->db->where('CAT','Blogs');
$query = $this->db->get();
Write a Stored Function to do the query. Then have Codeigniter merely do
query("SELECT PostRank(?,?)", $CAT, $POST_ID);
Restriction: Since you cannot do PREPARE inside a Stored Function, this function will necessarily be specific to one table, User_Posts.
I'm not entirely sure if this is the problem, but I'd be initialising #rownum in the subquery:
SELECT rank
FROM (
SELECT *,
#rownum:=#rownum + 1 AS rank
FROM $table
JOIN (SELECT #rownum := 0) init
WHERE CAT= ?
ORDER BY (Upvotes-Downvotes) DESC
) d
WHERE post_id = ?
Otherwise I'd be worried that #rownum is undefined (NULL) and stays that way while rank is calculated (NULL + 1 = NULL), only being assigned the value of 0 afterwards. Thus rank is returned as NULL and you get ['rank'=>].
Running this again in a constant connection (directly in MySQL) would then give you the correct result as #rownum would start from the value 0 from the previous query and rank would be calculated correctly.
I'm guessing codeigniter starts a new connection/transaction each time the query is run and #rownum starts at NULL each time, giving ['rank'=>].
BEFORE
id | cat_id | order
33 | 1 | 1
34 | 1 | 2
AFTER
id | cat_id | order
33 | 1 | 2
34 | 1 | 1
Now using 4 query
$db is wrap $mysqli for using placeholder and injection defense
get first record by id
$curr = $db->q('SELECT id,order,cat_id FROM `tbl` WHERE id`=? FOR UPDATE',
33)->fetch_assoc();
if exist first record find next record by order field
if($curr){
$next = $db->q('SELECT id,order FROM `tbl` WHERE `cat_id`=? AND
`order`>? ORDER BY `order` LIMIT 1 FOR UPDATE',
$curr['cat_id'],$curr['order']));
if exist first and second recorn change order value
if($prev['id']){
$db->q("UPDATE `tbl` SET `order`=? WHERE `id`=?",$next['order'],$curr['id']);
$db->q("UPDATE `tbl` SET `order`=? WHERE `id`=?",$curr['order'],$next['id']);
}
}
Important! Checking exist two record, lock rows for update
MySQL doesn't support update with the same table in the FROM statement. So because of this there are (select * from TBL) as t2 in inner subqueries.
Also EXISTS condition in the first CASE WHEN is to prevent update if the second record doesn't exists ("if exist first and second records change order value")
Here is a SQLfiddle example
UPDATE tbl as t1
SET `order`=
CASE WHEN id = 33
and
EXISTS (SELECT ID from (select * from TBL) t2 where
cat_id=t1.Cat_Id
and `order`>t1.`order`
ORDER BY `order`
LIMIT 1)
THEN
(SELECT `order` from (select * from TBL) t2 where
cat_id=t1.Cat_Id
and `order`>t1.`order`
ORDER BY `order`
LIMIT 1)
WHEN id <>33 THEN
(SELECT `order` from (select * from TBL) t2 where
cat_id=t1.Cat_Id
and `order`<t1.`order`
ORDER BY `order` DESC
LIMIT 1 )
ELSE `order`
END
where id =33
or
(SELECT ID from (select * from TBL) t2 where
cat_id=t1.Cat_Id
and `order`<t1.`order`
ORDER BY `order` DESC
LIMIT 1) =33
With one query it's:
UPDATE
`tbl`
SET
`order`=CASE
WHEN `order`=2 THEN 1
WHEN `order`=1 THEN 2
END;
WHERE
`order` IN (1,2)
or, for id's condition:
UPDATE
`tbl`
SET
`order`=CASE
WHEN `order`=2 THEN 1
WHEN `order`=1 THEN 2
END;
WHERE
id = $id
To swap 2 fields by row id try:
UPDATE `tbl` AS tbl1
JOIN `tbl` AS tbl2 ON ( tbl1.id = 33 AND tbl2.id = 34 )
SET
tbl1.order = tbl2.order, tbl2.order = tbl1.order
Also you can set your desired value instead of swap between 2 fileds.
If needed, you can add a where clause like below to swap where cat_id are 1 in two rows:
WHERE
tbl1.cat_id = 1 AND tbl2.cat_id = 1
Update:
If your order numbers are unique for any cat_id you can try this way:
UPDATE `tbl` AS tbl1
JOIN `tbl` AS tbl2 ON ( tbl1.order = 1 AND tbl2.order = 2 )
SET
tbl1.order = tbl2.order, tbl2.order = tbl1.order
WHERE
tbl1.cat_id = 1 AND tbl2.cat_id = 1
It works if your order field is int, Otherwise you should quote order values in query.
See the result on SQLFiddle
i need to get the latest order (from our custon admin panel). here's my query:
select *
from order
left join customer
on (customer.id = order.fk_cid)
where date = curdate()
order by time desc
limit 1;
this output everything from orders and customers which i need except 1 therefore that is why i use the *
here's my table structure:
order table:
id, fk_cid, date, time
customer table:
id, name, lastname, street, city, zip, country, phone, email, lastlogin
now, in my php i have:
$result = mysql_query("
select *
from `order`
left join customer
on (customer.id = order.fk_cid)
where date = curdate()
order by time desc
limit 1");
$row = mysql_fetch_assoc($result, MYSQL_ASSOC);
at this point my order is not correct, why?
Your customers.id is overwriting the order.id because you are using the same column name.
select *
from `order`
left join customer on (customer.id = order.fk_cid)
where date = curdate() order by time desc limit 1;
+------+--------+------------+----------+------+-------+------
| id | fk_cid | date | time | id | name | ....
+------+--------+------------+----------+------+-------+------
| 1 | 2 | 2011-11-30 | 07:01:23 | 2 | asasd | ....
+------+--------+------------+----------+------+-------+------
1 row in set (0.03 sec)
As you can see in this example you have two id, so PHP when retrieve the data using mysql_fetch_assoc it overwrites the second id because it's the same key in the array. To fix this, you will have to specify the columns in your query:
select `order`.id AS order_id, customer.id AS customer_id, customer.name /* etc... */
This will output:
Also, I recommend to use different name for your tables and fields. order, date, time since they are reserved word (in case you forget for use the ` ).
Array
(
[order_id] => 1
[customer_id] => 2
// etc...
)
Also here's a topic you should read: Why is SELECT * considered harmful?
Lets say i have a databse:
+----------+
| Database |
+----------+
| id |
| image |
| category |
+----------+
Now i have a page that shows an image from the database, i want to add a
<< Previous image
and
Next image >>
button. I could just take the $id and add +1 , but what if the next ID does not exist in the DB ?
Any help appreciated, thanks
So i found this:
SELECT *
FROM database AS c
WHERE (id = (SELECT MAX(id) FROM database WHERE id < c.id AND language = 'en')
OR id = (SELECT MIN(id) FROM database WHERE id > c.id AND language = 'en'))
But how do i make a link out of it, like:
Next ?
You'll have to use another select:
SELECT
( SELECT ID FROM <TABLE-NAME> WHERE ID > $currentID ORDER BY ID ASC LIMIT 1 )
AS NEXT_VALUE,
( SELECT ID FROM <TABLE-NAME> WHERE ID < $currentID ORDER BY ID ASC LIMIT 1 )
AS PREV_VALUE
FROM DUAL;
As explained in this answer, you can use a subselect query to get the ID of the previous and next records:
...
WHERE id IN (
'$id',
(SELECT MAX(id) FROM yourTable WHERE id < '$id'),
(SELECT MIN(id) FROM yourTable WHERE id > '$id')
)
...